In wireless systems where a common access point, such as a base station, communicates with multiple mobile terminals, there is a need to manage activity of the mobile terminals and allocation of resources. Since many mobile terminals are battery operated, there is a constant effort to minimize power consumption and optimize battery life. Accordingly, the mobile terminals often cycle between an active mode during communication sessions and one or more standby modes between communication sessions. While in a standby mode, the mobile terminals may operate in different ways depending on the communication system. For example, a mobile terminal may power down in standby mode and periodically power up and communicate with the base station to see if a communication session is necessary. When the mobile terminal awakes to see if a communication session is necessary, the mobile terminal is not considered in an active mode, and communicates with the access point only to a limited extent to determine if it should transition to an active mode.
During active modes, communication resources are allocated to facilitate communications between the mobile terminal and the access point. Unfortunately, the access point has limited communication resources and is limited in the number of mobile terminals with which it can communicate at any given time. Given these limitations, access points in current wireless communication systems control the operating mode of the mobile terminals and allocation of communication resources available for communications with the mobile terminals.
The communication resources correspond to the physical layer resources facilitating communication in a given communication medium. The communication resources are managed using a medium access control (MAC) protocol, which is typically a layer two protocol. Communications are effected using a data channel for communicating data traffic and a control channel for communicating control signaling according to the MAC protocol.
FIG. 1 illustrates the basic communication process of existing wireless systems wherein the mobile terminals are transitioned between active and standby modes. The control signaling by the access point controls transitions between the active and standby modes. During an active mode for a given mobile terminal, the access point sets an active-to-standby timer upon completion of either transmitting or receiving a block of data, TSET. The active-to-standby timer has a fixed value tTIMER. which corresponds to a defined period of time. If new data arrives for communication prior to expiration, the active-to-standby timer is cancelled, TCAN, the mobile terminal remains in the active mode, and the data is communicated. Once the data is communicated, the active-to-standby timer is once again set, TSET, using the fixed value, tTIMER.
If no new data needs to be communicated during the fixed period, the fixed active-to-standby timer expires, TEXP, and the access point instructs the mobile terminal to transition into the standby mode. When new data arrives for communication, TDATA, the access point instructs the mobile terminal to transition into the active mode. Notably, there is normally a certain amount of time, tTRAN, necessary for the mobile terminal to transition into an active mode and for the access point to recognize the mobile terminal is active and to allocate resources for facilitating communications between the mobile terminal and the access point. Once the mobile terminal returns to the active mode and the access point allocates the resources, TALLOC, the new data is communicated and the cycle will repeat as necessary.
As noted, the active-to-standby timer value tTIMER is set as a fixed configuration parameter and does not change dynamically during operation or among mobile terminals. A fixed timer value has proven satisfactory for traditional voice and low speed data systems where all traffic is processed with the same priority and treated equally. In such systems, a best effort approach is applied to all data regardless of type or user. However, higher speed data communications often prioritize certain types of data and users in different ways. For instance, voice or streaming media is prioritized over basic data transfer. Accordingly, a concept of quality of service (QoS) is necessary to control the tolerable transmission delay for data or the acceptable residual error rate.
In a system that delivers multiple levels of QoS, the data should not be treated equally, because the higher QoS users need more chances to communicate than the lower QoS users. The QoS requirements become apparent when the system is busy. If the same active-to-standby timer value tTIMER is equally applied to the higher QoS and the lower QoS users, there are equal chances for both QoS groups to be transitioned from the active mode to the standby mode. Once a user is moved from the active state to the standby state, it usually takes a significant amount of time, TTRAN, to transition back to the active mode. As a result, the data requiring a higher QoS is unacceptably delayed, even though the data requiring a lower QoS could tolerate even longer delays than that imposed.
Applying a shorter active-to-standby timer period for systems handling heavy traffic loads often results in urgent traffic suffering from unacceptable delays. These delays are imposed because the mobile terminals are transitioned prematurely into a standby mode and the time to transition back to the active mode is relatively long. Further, the fixed active-to-standby timer period does not allow for prioritizing data and users requiring different QoS levels. Accordingly, there is a need for a way to control the transitioning from an active mode to a standby mode based on QoS requirements.